This invention relates to a document transfer device for transferring a document to a predetermined reading position of an image reading apparatus while sucking the document, and an image reading apparatus having the document transfer device.
Heretofore, there has been known an image reading apparatus having a document transfer portion in which a document is transferred while being sucked. As shown in FIG. 20A, the image reading apparatus of this type includes an image reading portion 900 formed of a contact glass 901 fixed substantially horizontally to cover an upper opening of a box-shape casing 915, and a reading unit 902 for reading the image on the document while moving along the contact glass 901 housed in the casing 915; and a document transfer portion 910 for transferring the document to a predetermined reading position while sucking the document located on an upper side of the contact glass 901. As shown in FIGS. 20A and 20B, the document transfer portion 910 includes an endless transfer belt 903 extended over rollers 911, 912, 913 and provided with a plurality of suction holes 906; a suction duct 905 provided with suction ports 907 in a rectangular shape along the suction holes 906 on an inner side (an upper side) of the endless transfer belt 903 in order to suck the document; and a suction fan 904 for sucking air in the suction duct 905 disposed on a side opposite to the contact glass 901.
In the image reading apparatus, by sucking the air in the suction duct 905 through an operation of the suction fan 904, the document is sucked at the suction holes 906 formed on the transfer belt 903 through the suction ports 907. Then, the document is transferred to the reading position by the endless belt 903 in an arrow direction in FIG. 20A through rotation of the rollers 911, 912, 913 driven by a drive unit (not shown), and the image on the document is read by moving the reading unit 902 in a state where the document is pressed against the contact glass 901.
However, for example, in the case of a glossy document like a photograph, if a space between the document and the contact glass is about a wavelength of light, a Newton ring is generated by interference between the light reflected from the document surface and the light reflected through the contact glass, so that a good image can not be obtained.
Also, in the above image reading apparatus, since the transfer belt covers the entire surface of the contact glass in a document transfer direction and the suction duct has a length longer than that of the document in the document transfer direction, the document transfer portion becomes large, resulting in a large apparatus.
Also, in the above image reading apparatus, since the contact glass is fixed substantially horizontally with respect to an installation surface of the apparatus, the contact glass needs to have an appropriate width larger than the document in order to read the document mounted on a surface thereof. Further, since the casing for fixing the contact glass requires a larger area than that of the contact glass in order to accommodate the moving reading unit, the installation area of the entire apparatus becomes large, so that the installation area can not be reduced despite recent demands for reducing the same.
In view of the above drawbacks, the present invention has been made, and an object of the invention is to provide a document transfer device and an image reading apparatus, in which the generation of the Newton ring is prevented and a size of the apparatus is small.
Another object of the invention is to provide an image reading apparatus, in which the generation of the Newton ring is prevented, the installation area of the apparatus is reduced and the good image can be obtained.
Further objects and advantages of the invention will be apparent from the following description of the invention.